The sun is getting ready to bear down on all of us this weekend. And we know you think you know everything you need to know about sunscreen. What kind, how much needed to protect yourself and your family. But we decided to ask cecilia vega to give us a reality check. We found some surprises. Reporter: We are a nation of beach lovers. The reality is, although one in five people will get skin cancer, most of us are willing to take our chances. Tell me you're wearing sunscreen. No. You're not! Reporter: But you buy expensive sunblock, so you're safe, right? Well, "consumer reports" found one of their highest rated sunscreens costs just $5 a bottle. And if a higher dollar amount isn't the answer, is a higher spf? Truth is, after spf 30, the higher you go, the level of protection barely changes. Spf 30 blocks about 97% of the sun's rays. While spf 50 offers 98% protection. Spf 100, only one point higher, 99%. Reporter: Dermatologists say almost no one uses enough. What if I told you that the recommended amount of sunscreen that you're supposed to put on before you come out here and sunbathe is a shot glass full of sunscreen? I didn't put a full shot glass. I would say I put on maybe the bottom of the shot glass. Reporter: How much exactly? Squeeze and squeeze and squeeze some more. The recommendation is one ounce of sunscreen for exposed skin. That's a lot of sunscreen. Reporter: Who does that? Nobody does that. Reporter: A family of four should go through nearly an entire bottle of sunscreen every two hours in the sun. Really? Gosh, that's a lot. Reporter: And what about those of us who think we're safe because we wear a t-shirt in the sun? A white cotton t-shirt offers a protection rating of spf 7 against the sun's cancer-causing uv rays. If the shirt gets wet, the protection drops to level three. The protection goes up, the darker the shirt. A green cotton t-shirt, level ten. A thick fabric in black or navy, upf 50. We asked dermatologists how they stay safe. And this is how skin doctors have their fun in the sun. Cecilia vega, abc news, los

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Putting Sunscreen to the Test

Consumer Reports ranks effectiveness of sunscreen brands.

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